Impact evaluation of green-grey infrastructure interaction on built-space integrity: an emerging perspective to urban ecosystem service.

This paper evaluates the role of urban green infrastructure (GI) in maintaining integrity of built-space. The latter is considered as a lateral ecosystem function, worth including in future assessments of integrated ecosystem services. The basic tenet is that integrated green-grey infrastructures (GGIs) would have three influences on built-spaces: (i) reduced wind withering from flow deviation; (ii) reduced material corrosion/degeneration from pollution removal; and (iii) act as a biophysical buffer in altering the micro-climate. A case study is presented, combining the features of computational fluid dynamics (CFD) in micro-environmental modelling with the emerging science on interactions of GGIs. The coupled seasonal dynamics of the above three effects are assessed for two building materials (limestone and steel) using the following three scenarios: (i) business as usual (BAU), (ii) summer (REGEN-S), and (iii) winter (REGEN-W). Apparently, integrated ecosystem service from green-grey interaction, as scoped in this paper, has strong seasonal dependence. Compared to BAU our results suggest that REGEN-S leads to slight increment in limestone recession (<10%), mainly from exacerbation in ozone damage, while large reduction in steel recession (up to 37%) is observed. The selection of vegetation species, especially their bVOC emission potential and seasonal foliage profile, appears to play a vital role in determining the impact GI has on the integrity of the neighbouring built-up environment.